TOI-815 b
Astrophysical Synthesis & Habitability Characterization
TOI-815 b is a confirmed sub-neptune exoplanet orbiting the star TOI-815, located approximately 194.8 light-years (59.71 parsecs) from the Solar System. First announced in 2024 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.1225% across the stellar disk), this world measures 2.94 Earth radii and has a measured mass of 7.6 Earth masses. Combining its mass and radius yields a mean bulk density of 1.65 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.88 g⊕ (8.63 m/s²), and an escape velocity of 18 km/s.
In its orbital architecture around TOI-815, TOI-815 b completes one full revolution every 11.197 Earth days at a semi-major axis of 0.0903 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 87.7 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.2 carries the world between 0.0722 AU at periapsis and 0.1084 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 686 K (+413°C / +775°F) and receiving 36.90 S⊕ (~50,221 W/m²), TOI-815 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-815 is classified as an orange K-type star of spectral type K3 V with an effective photospheric temperature of 4,869 K, a radius of 0.77 R☉, a mass of 0.776 M☉, an estimated bolometric luminosity of 0.299 L☉. Stellar evolution modeling indicates an estimated stellar age of 0.2 Gyr and a metallicity of [Fe/H] = -0.09 dex (near-solar heavy-element abundance). From Earth, TOI-815 shines at apparent V-band magnitude 10.217 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere. The TOI-815 system is a multi-planet architecture hosting 2 confirmed worlds, with TOI-815 b sharing its stellar neighborhood alongside TOI-815 c.
Methodology: Computed using the Schulze-Makuch et al. (2011) weighted metric comparing physical interior (radius, estimated density) and surface thermal regime (escape velocity, equilibrium temperature).
Discovery Facility: Transiting Exoplanet Survey Satellite (TESS) · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | TOI-815 |
| Spectral Type | K3 V |
| Effective Temp (Teff) | 4,869 K |
| Stellar Radius | 0.7700 R☉ |
| Stellar Mass | 0.7760 M☉ |
| Bolometric Luminosity | 0.299 L☉ |
| Metallicity [Fe/H] | -0.090 dex |
| Stellar Age | 0.200 Gyr |
| Apparent Magnitude | V: 10.217 · G: 9.940 |
| System Architecture | 2 Stars, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.090300 AU |
| Orbital Period | 11.197 days |
| Mean Orbital Velocity | 87.7 km/s |
| Orbital Eccentricity (e) | 0.20000 |
| Orbital Inclination (i) | 89.3600° |
| Mean Bulk Density | 1.65 g/cm³ (18 km/s vesc) |
| Insolation Flux | 36.9000 S⊕ (~50,221 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 194.800 LY (59.712 pc) |